1. Technical Field
The present disclosure relates to apparatus and methods for treating spinal conditions and, more particularly, to an expandable cage with a locking device for supporting adjacent vertebrae.
2. Background of Related Art
The human spine includes thirty-three vertebrae. The vertebrae interlock with one another to form a spinal column. Each vertebra has a cylindrical bony body (vertebral body), two pedicles extending from the vertebral body, a lamina extending from the pedicles, two wing-like projections extending from the pedicles, a spinous process extending from the lamina, a pars interarticularis, two superior facets extending from the pedicles, and two inferior facets extending from the lamina. The vertebrae are separated and cushioned by thin pads of tough, resilient fiber known as inter-vertebral discs. Inter-vertebral discs provide flexibility to the spine and act as shock absorbers during activity. A small opening (foramen) located between each vertebra allows passage of nerves. When the vertebrae are properly aligned, the nerves pass through without a problem. However, when the vertebrae are misaligned or a constriction is formed in the spinal canal, the nerves get compressed and may cause back pain, leg pain, or other neurological disorders.
Disorders of the spine that may cause misalignment of the vertebrae or constriction of the spinal canal include spinal injuries, infections, tumor formation, herniation of the inter-vertebral discs (i.e., slippage or protrusion), arthritic disorders, and scoliosis. In these pathologic circumstances, surgery may be tried to either decompress the neural elements and/or fuse adjacent vertebral segments. Decompression may involve laminectomy, discectomy, or corpectomy. Laminectomy involves the removal of part of the lamina, i.e., the bony roof of the spinal canal. Discectomy involves removal of the inter-vertebral discs. Corpectomy involves removal of the vertebral body as well as the adjacent inter-vertebral discs.
A number of spinal surgical devices may be used to promote bony fusion after decompressing the spinal nerves. For instance, surgeons often replace the diseased vertebral tissue with one or more spinal cages and bone support matrix. Spinal cages support adjacent vertebral segments, while furthering spinal fusion of adjacent vertebral bodies. Scientists and clinicians have developed a number of devices and methods for decompressing spinal nerves. Improvements to this methods and devices are nevertheless still possible.